- Possible changes in the endocannabinoid profile, interacting with neuronal signaling for satiety and reward Nature and extent of the burden and risks associated with participation, benefit and group relatedness: This research is beneficial to the subjects, in that they all, being obese, will loose body-weight. Subjects included in the diet induced weight loss group will lose 10% of their initial weight, which is beneficial for the operation, as it will decrease the risk. This will however not compromise their possibility to undergo surgery if their BMI decreases below 35, as the intake for surgery is based upon the initial screening, proving that they are not able to be weight stable and that they already tried to be at a healthy stable weight with other weight loss methods. All participants will have to come visit the metabolic research unit Maastricht (MURM) on 4 different occasions, twice before the weight loss procedure and twice after. These visits will be combined with regular hospital visits as much as possible.